Here, the DarkSide-50 experiment at the Laboratori Nazionali del Gran Sasso is a search for dark matter using a dual phase time projection chamber with 50 kg of low radioactivity argon as target. ...Light signals from interactions in the argon are detected by a system of 38 photo-multiplier tubes (PMTs), 19 above and 19 below the TPC volume inside the argon cryostat. We describe the electronics which processes the signals from the photo-multipliers, the trigger system which identifies events of interest, and the data-acquisition system which records the data for further analysis. The electronics include resistive voltage dividers on the PMTs, custom pre-amplifiers mounted directly on the PMT voltage dividers in the liquid argon, and custom amplifier/discriminators (at room temperature). After amplification, the PMT signals are digitized in CAEN waveform digitizers, and CAEN logic modules are used to construct the trigger; the data acquisition system for the TPC is based on the Fermilab artdaq software. The system has been in operation since early 2014.
Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid ...argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~10^7, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon.
We present the results of a search for anomalous resonant production of tau lepton pairs with large invariant mass, the first such search using the CDF II Detector in Run II of the Tevatron pp ...collider. Such anomalous production could arise from various new physics processes. In a data sample corresponding to 195 pb(-1) of integrated luminosity we predict 2.8+/-0.5 events from standard model background processes and observe 4. We use this result to set limits on the production of heavy scalar and vector particles decaying to tau lepton pairs.
We report a measurement of the differential cross section dσ/d(cosθ(t)) for top-quark pair production as a function of the top-quark production angle in proton-antiproton collisions at sqrts = 1.96 ...TeV. This measurement is performed using data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.4 fb(-1). We employ the Legendre polynomials to characterize the shape of the differential cross section at the parton level. The observed Legendre coefficients are in good agreement with the prediction of the next-to-leading-order standard-model calculation, with the exception of an excess linear-term coefficient a(1) = 0.40 ± 0.12, compared to the standard-model prediction of a(1)=0.15(-0.03)(+0.07).
The mass and the total decay width of the W boson are measured with the L3 detector at the LEP e+e– collider using W-boson pairs produced in 0.7 fb–1 of data collected at centre-of-mass energies ...between 161 and 209 GeV. Combining semi-leptonic and fully-hadronic final states, the mass and the width of the W boson are determined to be where the first uncertainty is statistical and the second systematic.
We report a measurement of the difference (D/Acp) between time-integrated-violating asymmetries in D{sup 0} K{sup +}K{sup -} and D{sup 0} {pi}{sup +}{pi}{sup -} decays reconstructed in the full data ...set of proton-antiproton collisions collected by the Collider Detector at Fermilab, corresponding to 9.7 fb{sup -1} of integrated luminosity. The strong decay D*{sup +} D{sup 0}{pi}{sup +} is used to identify the charm meson at production as D{sup 0} or 'D{sup 0}. We measure D/Acp = (-0.62 0.21 /stat 0.10 /syst)%, which differs from zero by 2.7 Gaussian standard deviations. This result supports similar evidence for violation in charm-quark obtained in proton-proton collisions.
We present the results of a search for pair production of a heavy toplike (t') quark decaying to Wq final states using data corresponding to an integrated luminosity of 5.6 fb(-1) collected by the ...CDF II detector in pp collisions at √s=1.96 TeV. We perform parallel searches for t'→Wb and t'→Wq (where q is a generic down-type quark) in events containing a lepton and four or more jets. By performing a fit to the two-dimensional distribution of total transverse energy versus reconstructed t' quark mass, we set upper limits on the t't' production cross section and exclude a standard model fourth-generation t' quark decaying to Wb (Wq) with mass below 358 (340) GeV/c(2) at 95% C.L.
The DarkSide experiment aims to perform a background-free direct search for dark matter with a dual-phase argon TPC. The current phase of the experiment, DarkSide-50, is acquiring data at Laboratori ...Nazionali del Gran Sasso and produced the most sensitive limit on the WIMP-nucleon cross section ever obtained with a liquid argon target (2.0 × 10-44 cm2 for a WIMP mass of 100 GeV/c2). The future phase of the experiment will be a 20 t fiducial mass detector, designed to reach a sensitivity of ~1 × 10-47 cm2 (at 1 TeV/c2 WIMP mass) with a background-free exposure of 100 ty. Here, this work contains a discussion of the current status of the DarkSide-50 WIMP search and of the results which are more relevant for the construction of the future detector.
Using Zγ candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. Zγ couplings ...vanish at tree level and are heavily suppressed at higher orders; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb(-1) in the Z→νν¯ decay channel and 5.1 fb(-1) in the Z→l(+)l(-) (l=μ, e) decay channels. The combination of these measurements provides the most stringent limits to date on Zγ trilinear gauge couplings. Using an energy scale of Λ=1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Zγ couplings to be |h(3)(γ,Z)|<0.022 and |h(4)(γ,Z)|<0.0009. These results are consistent with standard model predictions.
PDF
